Recording and reproduction of moving pictures with or without the accompaniment of sound



Nov. 1, 1949 s. B. MORGAN ET AL 2,4$6,3b7

RECORDING AND REPRODUCTION OF MOVING PICTURES WITH OR WITHOUT THE ACCOMPANIMENT OF SOUND Filed Sept. 10, 194.6

Patented Nov. 1, 1949 RECORDING AND REPRODUCTiON OF MOV- ING PICTURES WITH OR WITHOUT THE ACCOMPANIMENT OF SOUND George Bernard Morgan, London, and Charles Norman Smyth, Botley, Oxford, England Application September 10, 1946, Serial No. 696,008 In Great Britain September 10, 1945 7 Claims. 1

This invention relates to the recording of moving pictures on discs and/ or reproducing them from such disc records in a stabilised form with or without the accompaniment of sound.

According to the present invention the pictures are recorded on the disc, not in their truerectangular shape but distorted on small radial segments limited by two arcs and two radial lines so that they are condensed in their lower parts, and their images are reflected by a cylindrical parabolic mirror which causes them to appear as true pictures of square or rectangular shape arranged in a straight line.

The disc is preferably driven at variable angular speed so as to keep the linear velocity of the reproducing point constant over the whole length of the spiral.

Where transmitted light is employed and opposite sides of the same part of the record are used to record vision and sound, translucent material is used, or the material is rendered translucent by surface or other treatment so as to diffuse the light and prevent a distorted image of the sound recording from being superimposed upon the picture. Alternatively, the record is made sufficiently thick to achieve the same purpose, Oblique lighting may be used to help secure these ends. Where light pick-up is used for both sound and vision programmes, transmitted light may be used for actuating one or both pick-up devices by the use of polarising screens or different-coloured lights and filters, even though they are recorded on opposite sides of the same part of the record.

The picture is projected on to the screen by means of a lens system of normal type and the screen may or may not be in one cabinet with the producer. Interposed between the record and the lens or between the lens and the screen, is a rotating mirror polygon which displaces the image in a direction perpendicular to the axis of the record in such a way as to produce a stationary picture from a continuously moving record. This technique is well-known and is described in a paper by F. Tuttle and C. 1. Reid in the Journal of the Optical Society of America, entitled The problem of motion picture projection from continuously moving film, (volume 22, February 1932, pages 39-64).

Systems of rotating lenses or refracting prisms may be used to the same end, as described in Tuttles paper. Where the term "polygon is mentioned, this is preferred. It is however to be understood that in the present invention other well known optical equivalents may be used.

Referring more particularly to the reproduction of moving pictures photographically recorded and arranged in succession spirally on the surface of a disc, these pictures move along the arc of a circle durin the rotation of the record and an angular distortion takes place, i. e. the picture rotates as it is being reproduced.

The mirror polygon used in conjunction with the rotating disc record for the purpose of reproduction produces a stationary image, the mirror cancelling out the movement of translation; however, the angular rotation that the picture has suffered is not thereby corrected.

According to the invention the angular distortion is corrected by projecting on the screen, not the actual picture from the disc, but an image thereof as seen in the cylindrical parabolic mirror.

In the accompanying drawings, Figure 1 is an explanatory diagram of the use of the cylindrical parabolic mirror, and

Figures 2 and 3 are respectively a plan view and part sectional elevation of one construction of the device according to the present invention.

It is a well-known property of the parabolic reflector that it causes parallel beams of light to converge at its focal point. Consequently (see Figure 1), if we imagine a circular disc a marked with radial lines placed with its centre 2) at the focus of a parabolic mirror 0 the radial lines d will appear as parallel lines d when viewed in the mirror. Furthermore, concentric circles about the focal point will appear as parallel lines perpendicular to the radial lines. S0, if the pictures are recorded on small radial segments e of the disc and appropriately distorted by being so to say condensed in the lower part of the se ments, then their images reflected by the parabolic mirror will appear as true pictures in square or rectangular frames f arranged in a straight line. Use may be made of astationary parabolic mirror the curvature of which would be such as will straighten out the curvature of the middle part of the record in the reflected image.

The use of a parabolic mirror placed as above referred to would necessitate a long focal length since the image would be far behind the mirror. In order to be able to use a short focus lens and consequently high magnification, according to a further feature of the invention a relative movement is effected between the mirror and the centre of the record, during the rotation of the latter, its lower edge being kept nearly level with and close to the outer edge of the picture element that is being projected.

In this modification, if the focal point of the mirror is to remain at the centre of the disc during its rotation, the curvature of the mirror must be changed as it is continuously shifted. For this purpose use is preferably made of a mirror consisting of a surfaced steel strip which is continuously bowed during the reproduction. The bowing may be effected by mounting the mirror between two stout supports, the distance between which is varied automatically by means of a cam. Such an arrangement will effect a change of curvature which is sufliciently accurate for most purposes. In order to obtain a greater parabolic precision, if necessary, use may be made of a strip of steel the thickness of which varies towards the edges engaging in the movable su ports.

The parabolic mirror may be tilted forwards towards the centre of the record at an angle of approximately 45 so that the image is produced in a vertical lane, thereby enabling the polygon to be rotated in a horizontal plane. This arrangement permits of the projection being effected without interruption of the light beam by the record.

The optical system necessary to proiect the reflected image does not differ materially from that renuired for projecting normal cinematograoh film.

In the descri tion to follow only the fundamental parts of this mode of carrying the invention into effect are referred to and it is to be understood that the practical constructions will include additional features, such as means to enable the record to be changed quickly, e. g. special clips or catches to hold the record rigidly in its mounting and release it quickly, and devices to enable several records to be lodged in the reproducer together and then to be played in suitable sequence automatically or designed to enable a new record to be fitted in and be ready for use while the preceding one is still being played. Arrangements for storing the records may also be incorporated with the reproducer and the reproducer may be designed to accommodate records of various diameters in order that they may be stored one within the other.

Referring to Figures 2 and 3, the disc record I is placed on a turntable 2 mounted on a fixed shaft and driven by a constant velocity drive comprising a driving drum 6, a helically stepped pulley 3 mounted on the fixed shaft 5 of the turntable; and a driving steel tape 1 one end of which is secured to the drum 6 and the other to the pul ey 3, a spring 4 within which ensures a quick return when the drive is released. The drum 6, which may be similarly, but less strongly, spring loaded for the same purpose, is mounted on a shaft 9 driven by a worm wheel I2 operated by a worm IS. The drum is prevented from overrunning and slackening the tape by means of a friction pad provided on the drum shaft or by an electromagnetic clutch (not shown).

8 is a guide for the steel tape 1 and also for phase adjustment to cause the tape to take a slightly longer or shorter path, the latter adjustment being effected by a displacement along a slot H by means of a knob ID. This phase adjustment may be efiected automatically by photoelectric control from the picture position and by using a solenoid operating device. The displacement of the tape in the axial direction of the pulley 3 is efiected by causing the guide to be 4 shifted along by the screw-thread 8 which is rotated by the drum 6 through a gear 3', 3".

The drive of the turntable by means of a helically stepped pulley and steel tape will rotate the record at a constant linear velocity. Other types of drive may be used for the same purpose, such as a small pinion or rubber wheel driving the turntable from underneath at a constantly varying distance from the centre.

A parabolic mirror [6 is slantingly held over the record I between two supports l6, l6", mounted on a moving carriage H, at least one of which supports is adapted to be automatically moved towards the other support during the rotation of the disc record and thereby bow the mirror IS with a view to changing its curvature as required. The movable support l6 may be constituted by one arm of a two-arm lever 2| pivoted at 26 on the movable carriage ll, the other arm of which lever abuts by means of a cam follower 23 aga nst a stationary cam surface 22, so designed that when the carriage ll carrying the parabolic mirror I6 is moved towards the centre of the record the arm with the cam follower 23 will be forced outwards, and the arm engaging the mirror will move inwards, thereby bowing the latter as required.

The translational movement of the carriage I1 is effected along guiding grooves 24 in the base A of the apparatus by means of worm and reduction gear i8, l8, l8" and of a toothed rack 21 on the carriage in engagement with the pinion I8" of the reduction gear. The gear moving the carriage and the gear associated with the shaft of the drum 6 on which the steel tape 1 is wound are mechanically interconnected by means of the worm shaft l9 held in quick release brackets 20 adapted to be mechanically or electrically operated to enable the parts to return to the initial positions automatically at the end of the record, or before if desired.

A mirror polygon I5, which may be provided with say about 40 faces, is driven through a reduction gear l3 and pulley 25 (not shown) in synchronism with the other movements above referred to. In addition thereto a translation movement has to be effected between the centre of the mirror polygon and the centre of the turntable.

For this purpose the mirroi polygon is carried along by the moving carriage and use is made of a flexible drive it, such as a constant velocity cable or flexible tube (e. g. Tombac electrical drive, or belt or chain with suitable jockey pulley.

The parabolic mirror producing the images of the pictures and reflecting them onto the mirror polygon, the latter, and the lens 28 receiving the reflected images from the polygon to project them onto the screen are all moved together by the moving carriage l1.

The sound record may be provided on the same disc as the pictures, but preferably on a separate disc, and be reproduced from a separate and suitably synchronised turntable.

Instead of the carriage with the parts mounted thereon being moved relatively to the other parts, the latter may be displaced relatively to the carriage, which is kept in a fixed position in order to keep the screen at a constant distance from the lens.

Diificulty in reproduction may be experienced if the record does not run quite true, due, for example, to its being bent. This may be overcome by providing the reproducing, and if necessary recording head, with a hinged and counterbalanced mounting and a skid which ridesupon the record surface and maintains the lens exactly at the desired constant distance from the record. Alternatively the diiliculty may be overcome by constructing the record of a slightly pliable material or providing it with a slightly flexible mounting and causing it to rotate over a guide so that the part of the record being reproduced is always at a constant distance from the lens.

The details for carrying the invention into effect may otherwise be modified without departing from its scope.

We claim:

1. A device for reproducing moving pictures by means of a disc record on which pictures of segment shape are arranged in succession spirally, each picture being distorted by being radially condensed in the lower part of the segments, comprising means for driving the said record, optical means for projecting images of the pictures and stabilising them and a cylindrical parabolic reflecting surface interposed in the optical path of the optical means, whereby the images of the said pictures are reflected in a straight line and the distortions are corrected.

2. A device for reproducing moving pictures as claimed in claim 1 in which the disc record is of translucent material on which the pictures are recorded on one face and sound is recorded on the other face, in order to diffuse the light and thereby prevent a distorted image of the sound recording from being superimposed upon the pictures.

3. A device for reproducing moving pictures as claimed in claim 1 in which the cylindrical parabolic reflecting surface has a curvature which will straighen out the curvature of the middle part of the record in the reflected image.

4. A device for reproducing moving pictures as claimed in claim 1 comprising means for moving the cylindrical parabolic reflecting surface radially with respect to the record for the pur-. pose of following the picture elements as they are being reproduced.

5. A device as claimed in claim 1 comprising means for moving the cylindrical parabolic reflecting surface radially with respect to the record and gradually reducing its radius of curvature during its movement for the purpose of following the picture elements as their radius of rotation is decreasing.

6. A device for reproducing moving pictures as claimed in claim 1 in which the cylindrical parabolic reflecting surface consists of a surfaced spring leaf of thickness varying towards the side edges in combination with means for bowing it during the traverse of the record for the purpose of following the picture elements as their radius of rotation is decreasing.

7. A device for reproducing moving pictures as claimed'in claim 1 in which the cylindrical parabolic reflecting surface is tilted forwardstowards the centre of the record at an angle of approximately for the purpose set forth.

GEORGE BERNARD MORGAN. CHARLES NORMAN SMYTH.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,728,986 Stokes Sept. 24, 1929 1,864,519 Boularan June 28, 1932 1,933,057 Harkin Oct. 31, 1933 2,005,914 Freund June 25, 1935 2,128,078 Davis Aug. 23, 1938 2,203,437 Levy June 4, 1940 2,299,738 Collins Oct. 27, 1942 2,346,472 Continer Apr. 11, 1944 

